italki's users have had different experiences on Skype, some of them good and another not much, well that is my case.
There are some of my reasons why I have removed some people there:
1- I have felt uncomfortable.
2- I don't like their way to practice.
3- It's impossible to have a conversation with them (some teenagers for example).
4- They didn't show interest to talk so, I got bored.
5- They have been offensive talking about Latin countries (They feel higher).
6- They have been offensive to me.
About the number 6, I think I don't need to say something in situations like that, do I?
About the rest of reasons, what do you think? Maybe, you have had another experience. Should we give them a reason why?
Up to you, if you feel that you can give some constructive criticism, about things on which the people can work on, and it's not blatantly mean, you can try to explain yourself before leaving, as long as you make it clear that you already made your decision. But it's hard to react positively to it, so it's really up to you if you want to face possible backslash, like an angry outburst or some bitter comment.
At least in my experience, it's common for people to stop replying, even after a year of talking, and when there's no explanation it makes me ask myself if it was something wrong with me (e.g. is my English not good enough? Was I boring?), eventually after a while I just prefer to cut ties and stop worrying. If someone tells me they don't have time to practice anymore it's way easier, we become Facebook friends who talk a couple of times a year, so in that sense I appreciate people using words, but I can survive someone ghosting me, any day of the week.
If you have been talking to someone for months, I think at least trying to address the problem would be good for both of you (for you to practice addressing things that bother you, as we can't always just cut off people).
I have some experience to talk by video call in Wechat, not Skype, but I think it's the same idea.
The reasons 3 and 4 of your list are the most relevant for me. And the 5 recently, because the olympic games have been in my city and a lot of people said things that not true. But I resist to remove them.
I guess sometimes it's like a challenge find a person to talk.
A lot of men won't talk with others men, just with girls (yeah, it's stupidity), and a lot of girls know need to take care to talk with a man because a lot of men do idiotic things on chat. So, It's hard find someone to just talk.
So, I just remove people that do offensive things.
Sorry for my mistakes. My English is bad yet.
Number 4 is a frequent reason for me. When I started on italki, I collected a lot of skype names from people who said they wanted to talk. But then nothing happened and we never talked at all, so eventually I removed those people I never heard from again.
Later I changed my approach and told people that I was looking for regularly scheduled conversations, usually once a week, and then only added people I could make an appointment with. That works better for me than "spontaneous" chats on skype which either never happen or distract me while I'm working.
EDIT: I never told those people that I was deleting them, but as I said, I never spoke to them on skype so I don't feel too bad about it.
And I have one funny situation :)
There is one guy who I talked only once but during this conversation I couldn't say a word :)
He was talking and talking and talking and even if he asked me some question I began to answer and he interuppted me and talked again :))
So now he wants to speak with me again and I don't see the sense. And I can't find a reason to stop communicate with him and just delete him will be very rude.
Do you have any ideas? :))
You know my feelings about the point number 5!
You're right. Finding a person who you can practice with, it's a challenge. Some men are looking for other things here so, women need to be careful, I think that is a little contradictory though because in my case, I have sent message to other women and I haven't received anything so, I have to send message to men and it has become something difficult to me, I would like to talk with women. Fortunately, all my men friends that I have right now on Skype have been really sweet to me (with an exception of two that I'll remove haha because I've never talked with them)